Phenyldioxanes

ABSTRACT

PCT No. PCT/EP90/02132 Sec. 371 Date Feb. 12, 1991 Sec. 102(e) Date Feb. 12, 1991 PCT Filed Dec. 8, 1990 PCT Pub. No. WO91/09026 PCT Pub. Date Jun. 27, 1991.Phenyldioxanes of the formula I   &lt;IMAGE&gt; I wherein R1 is an alkyl or alkenyl residue each with up to 16 C atoms, wherein one or two non-adjacent CH2 groups of these residues may be replaced by -CO-O- or -O-CO-, Q1 and Q2 are each independently &lt;IMAGE&gt;  &lt;IMAGE&gt;  &lt;IMAGE&gt;  L1 and L2 are each independently F or H, and Y is Cl, F, CN, CF3, OCF3 or OCF2H, m and n is 0 or 1, are suitable as components of liquid crystal media.

The invention relates to Phenyldioxanes of the formula I ##STR3## wherein R¹ is an alkyl or alkenyl residue each with up to 16 C atoms, wherein one or two non-adjacent CH₂ groups of these residues may be replaced by --O--, --S--, --CO--O-- or --O--CO--,

Q¹ and Q² are each independently ##STR4##

L¹ and L² are each independently F or H, and

Y is Cl, F, CN, CF₃, OCF₃ or OCF₂ H,

m and n are 0 or 1

with the provisos that

a) in the case m and n are O, L¹ is F and Y is Cl, F, --CF₃, --OCF₃ or OCF₂ H or L¹ and L² are H and Y is Cl or F.

b) in the case that n is O, m is 1 and Q¹ is ##STR5## one of L¹ and L² is F and Y is Cl, F, CF₃, OCF₃ or OCF₂ H, and

c) in the case that n is 1 and m is O and Q² is ##STR6## one of L¹ and L² is F or L¹ and L² are H and Y is Cl, --CF₃, --OCF₃ or --OCF₂ H.

The compounds of the formula I can be used as components of liquid crystal media, in particular for displays which are based on the principle of the twisted nematic cell, including TN cells with a higher twist angle like STN, SBE, OMI etc., on the guest-host effect on the effect of deformation of orientated phases or on the effect of dynamic scattering.

Compounds similar to those of formula I are known from DE 29 44 905. These compounds comprising 2 rings but no terminal chlorine tend to reduce the mesophase range.

JP-57 064 689 describes ##STR7##

Compounds of the formula I with three rings and L=H or F are claimed in EP 0 087 679 and EP 0 154 840 via a very broad formula. There are, however, no specific examples for these compounds so that it may be stated that the surprisingly advantageous properties of these compounds have neither been realized nor used.

Similar phenyldioxanes with terminal OCF₃ -group but without ethyllinhage are known from WO 89 02 884.

WO 87/06602 describes ##STR8## and

WO 90/01056 describes ##STR9##

Furthermore ethyl-linked phenyldioxanes with a negative or neutral value of the dielectricity are known: ##STR10##

EP-0 154 840.

The invention was based on the object of discovering new stable liquid crystalline or mesogenic compounds which are especially suitable for active matrix displays without exhibiting the shortcomings of the prior art compounds.

Surprisingly, it has been found that the compounds according to formula I meet these criteria to an outstanding degree and allow the realization of a very high resistivity and simultaneously favorable electro-optic characteristics. These compounds also show a surprisingly good solubility at -20° C. in many LC base materials from other compound classes.

By providing the compounds of the formula I, the range of liquid crystal substances which are suitable, under various technological aspects for the preparation of nematic mixtures is also quite generally widened considerably.

The compounds of the formula I have a wide field of application and they are preferably added to liquid crystal base materials from other classes of compounds, for example in order to increase the clearing point while having little effect on other physical properties.

The compounds of the formula I are colourless in the pure state and form liquid crystal mesophases in a temperature range which is favorably placed for electrooptical use. They are sufficiently stable towards chemicals, heat and light.

The invention thus relates to the compounds of the formula I in particular to the compounds of the formula I1, ##STR11## wherein R¹, Q², L¹ and Y have the meaning given and Y is Cl or in the case that one of L¹ and L² is F also F, in particular, wherein Q² is 1,4-phenylene and n is 1 and Y is Cl, and furthermore to the compounds of the formula I2 ##STR12## wherein R¹, L² and Y have the meaning given o is 0 or 1, and ##STR13## with the proviso that in the case that o is O Y is different form CN and one of L¹ and L² is F.

Furthermore the invention relates to the use of these compounds as components of liquid crystal media. The invention furthermore relates to liquid crystal media containing at least one compound of the formula I and to liquid crystal display elements, in particular electrooptical display elements, which contain media of this type.

The compounds of the formula I are in particular suitable as compounds of liquid crystal media for displays which are based on the principle of polymer dispersed (pdlc) or polymer network (pn) liquid crystals due to their favorable optical anisotropy and their dielectric anisotropy.

Above and below R¹ has the mentioned meaning, unless expressly stated otherwise.

The compounds of the formula I1 accordingly include compounds of the part formulae I1a to I1h: ##STR14## The compounds of the formulae I1c and I1d are particularly preferred.

The compounds of the formula I2 include ethyl-linked phenyldioxanes of the formula I2a to I2f: ##STR15##

Y is Cl, F, CN, CF₃ or OCF₃ ; in the laterally fluorinated compounds of the formulae I2c, I2d and I2f Y denotes preferably F, Cl or CN.

In the compounds of the formulae I2a, I2b and I2c Y denotes preferably Cl, CF₃ or OCF₃.

The compounds of the formulae I2 include phenyldioxanes without ethyl-linkage of the formulae I2g to I2n: ##STR16## The compounds of the formulae I2g to I2j wherein ##STR17## are particularly preferred.

R¹ is preferably alkyl, alkoxy, oxaalkyl or alkenyl and can exhibit a straight-chain or branched structure.

Alkyl or alkoxy preferably are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms. Accordingly they are preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy. Oxaalkyl is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or 3-oxybutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8-, or 9-oxadecyl.

In the compounds of these formulae R¹ is preferably alkyl, furthermore also groups in which one CH₂ group is replaced by oxygen.

If R¹ is alkyl and/or alkoxy group, these can be straight-chain or branched. Preferably, they are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms and are accordingly preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, methoxy, octoxy or nonoxy.

The compounds of the formula I1a, wherein R¹ is Ethyl, n-Butyl, n-Pentyl or n-Hexyl, are particularly preferred. As a rule they are suitable to lower the threshold voltage of liquid crystal mixtures.

Oxaalkyl is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or 3-oxybutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl or 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl.

Compounds of the formula I with branched terminal group R¹ can be of importance because of a better solubility in the customary liquid crystal base materials, but in particular as chiral doping substances if they are optically active.

Branched groups of this type as a rule contain not more-than one chain branching. Preferred branched groups are isopropyl, 2-butyl (=1-methylpropyl), isobutyl (=2-methylpropyl), 2-methylbutyl, isopentyl, (=3-methyl- butyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 1-methylheptoxy (=2-octyloxy), 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl and 6-methyloctoxy.

In the case of compounds with branched terminal groups, formula I includes both the optical antipodes and racemates as well as mixtures thereof.

Of the compounds of the formula I and subformulae thereof, those in which at least one of the radicals contained therein has one of the preferred meanings given are preferred.

The compounds of the formula I are prepared by methods which are known per se, such as are described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der Organischen Chemie Methods of Organic Chemistry, Gerog-Thieme-Verlag, Stuttgart), and in particular under reaction conditions which are known and suitable for the reactions mentioned. Variants which are known per se and are not mentioned in more detail here can also be used in this connection.

If desired, the starting substances can also be formed in situ, such that they are not isolated from the reaction mixture but are immediately reacted further to give the compounds of the formula I.

The preferred synthetic routes are shown in the following schemes I to III: ##STR18##

A preferred route for preparation of the ethyl-linked phenyldioxanes of the formula I2 is shown in the following scheme IV: ##STR19##

A preferred route for preparation of phenyldioxanes of the formula I2 without ethyl-linkage is shown in the following scheme V: ##STR20##

All starting materials are known or prepared in analogy to known starting materials.

All steps are fully conventional and the reaction conditions are known to the skilled worker. The starting materials are known or easily prepared in analogy to known materials.

Other methods of making compounds of formula I are apparent to those skilled in the art.

In addition to one or more compounds of formula I the liquid crystal media according to the invention preferably contain 2-40 components and in particular 4-30 components. Liquid crystal media being composed of one or more compounds of formula I and 7-25 other components are especially preferred.

These additional components are preferably chosen from the nematic or nematogenic (monotropic or isotropic) substances; in particular from the classes of azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates, phenyl or cyclohexyl cyclohexylbenzoates, phenyl or cyclohexyl cyclohexylcyclohexanecarboxylates, cyclohexylphenylbenzoates, cyclohexylphenyl cyclohexanecarboxylates, cyclohexylphenyl cyclohexylcyclohexanecarboxylates, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexyleyclohexanes, cyclohexylcyclohexanes, cyclohexyleyclohexenes, cyclohexylcyclohexylcyclohexene, 1,4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes, 1,2-diphenylethanes, 1,2-dicyclohexylethanes, 1-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2-(4-phenyl-cyclohexyl)-ethanes, 1-cyclohexyl-2-biphenylethanes, 1-phenyl-2-cyclo- hexyl-phenylethanes, optionally halogenated stilbenes, benzyl phenyl ethers, tolanes and substituted cinnamic acids.

The 1,4-phenylene groups of these compounds may be fluorinated.

The most important compounds which are possible constituents of liquid crystal media according to the invention can be characterized by the formulae 1, 2, 3, 4 and 5:

    R'--L--E--R"                                               1

    R'--L--COO--E--R"                                          2

    R'--L--OOC--E--R"                                          3

    R'--L--CH.sub.2 CH.sub.2 --E--R"                           4

    R'--L--C--C--E--R"                                         5

In the formulae 1, 2, 3, 4 and 5 L and E may be equal or different from each other. L and E independently from each other denote a bivalent residue selected from the group consisting of --Phe--, --Cyc--, --Phe--Phe--, --Phe--Cyc--, --Cyc--Cyc--, --Pyr--, --Dio--, --G--Phe--, --G--Cyc-- and their mirror images; in this compilation of residues Phe denotes unsubstituted or fluorinated 1,4-phenylen, Cyc trans- 1,4-cyclohexylene or 1,4-cyclohexenylen, Pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio 1,3-dioxane-2,5-diyl and G 2-(trans-1,4-cyclohexyl)-ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.

One of the residues L and E is preferably Cyc, Phe or Pyr. E preferably denotes Cyc, Phe or Phe--Cyc. The liquid crystal media according to the invention preferably contain one or more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with L and E meaning Cyc, Phe and Pyr, said liquid crystal media further containing at the same time one ore more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with one of the residues L and E denoting Cyc, Phe and Pyr and the other residue being selected from the group consisting of --Phe--Phe--, --Phe--Cyc--, --Cyc--Cyc--, --G--Cyc--, said liquid crystal media containing in addition to this optionally one or more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with L and E being selected from the group consisting of --Phe-Cyc--, --Cyc--Cyc--, --G--Phe-- and --G--Cyc. In a preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5 (subgroup 1) R' and R" are independently from each other alkyl, alkenyl, alkoxy, alkenoxy with up to 8 carbon atoms. R' and R" differ from one another in most of these compounds, one of the residues usually being alkyl or alkenyl. In another preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5 (subgroup 2) R" denotes --CN, --CF₃, --OCF₃, --OCHF₂, --F, --Cl or --NCS while R' has the meaning indicated in subgroup 1 and is preferably alkyl or alkenyl. Other variants of the envisaged substituents in the compounds of formulae 1, 2, 3, 4 and 5 are also customary. Many such substances are commercially available. All these substances are obtainable by methods which are known from the literature or by analogous methods.

The liquid crystal media according to the invention preferably contain in addition to components selected from subgroup 1 also components of subgroup 2, the percentage of these components being as follows:

subgroup 1: 20 to 90%, in particular 30 to 90%

subgroup 2: 10 to 50%, in particular 10 to 50%

In these liquid crystal media the percentages of the compounds according to the invention and the compounds of subgroup 1 and 2 may add up to give 100%.

The media according to the invention preferably contain 1 to 40%, in particular 5 to 30% of the compounds according to the invention. Media containing more than 40%, in particular 45 to 90% of the compounds according to the invention are further preferred. The media contain preferably 3, 4 or 5 compounds according to the invention.

The media according to the invention are prepared in a manner which is customary per se. As a rule, the components are dissolved in one another, advantageously at elevated temperature. The liquid crystal media according to the invention can be modified by suitable additives so that they can be used in all the types of liquid crystal display devices. Such additives are known to the expert and are described in detail in the literature (H. Kelker/R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, it is possible to add pleochroic dyestuffs to prepare colored guest-host systems or substances for modifying the dielectric anisotropy, the viscosity and/or the orientation of the nematic phases.

The following examples are to be construed as merely illustrative and not limitative. m.p.=melting point, c.p.=clearing point. In the foregoing and in the following all parts and percentages are by weight and the temperatures are set forth in degrees Celsius. "Customary work-up" means that water is added, the mixture is extracted with methylene chloride, the organic phase is separated off, dried and evaporated, and the product is purified by crystallization and/or chromatography.

Further are:

C: crystalline-solid state, S: smectic phase (the index denoting the typ of smetic phase), N: nematic phase, Ch: cholesteric phase, I: isotropic phase. The number being embraced by 2 of these symbols denotes the temperature of phase change.

EXAMPLE 1

According to Scheme I given above 4-(5-propyldioxan-2-yl)-chlorobenzene is obtained from p-bromochlorobenzene and 2-(hydroxymethyl)-pentan-1-ol, C 72 I, Δε=8.6.

EXAMPLES 2 TO 20

The following compounds are prepared analogously

    __________________________________________________________________________     R.sup.1      n Q.sup.2 L Y                                                     __________________________________________________________________________     (2)                                                                               C.sub.5 H.sub.11                                                                         0 --      H Cl, K 66 I, Δε = 7.0                    (3)                                                                               C.sub.7 H.sub.15                                                                         0 --      H Cl                                                    (4)                                                                               C.sub.3 H.sub.7                                                                          0 --      F Cl, C 33 I, Δε = +11.8                  (5)                                                                               C.sub.5 H.sub.11                                                                         0 --      F Cl, C 30 I, Δε = 9.5                    (6)                                                                               C.sub.7 H.sub.15                                                                         0 --      F Cl                                                    (7)                                                                               C.sub.3 H.sub.7                                                                          0 --      F F                                                     (8)                                                                               C.sub.5 H.sub.11                                                                         0 --      H F, C 25 I, Δε = +7.7                    (9)                                                                               C.sub.7 H.sub.15                                                                         0 --      H F, C 15 I, Δε = +6.9                    (10)                                                                              C.sub.3 H.sub.7                                                                          1                                                                                 ##STR21##                                                                             H Cl                                                    (11)                                                                              C.sub.5 H.sub.11                                                                         1                                                                                 ##STR22##                                                                             H Cl                                                    (12)                                                                              C.sub.7 H.sub.15                                                                         1                                                                                 ##STR23##                                                                             H Cl                                                    (13)                                                                              C.sub.3 H.sub.7                                                                          1                                                                                 ##STR24##                                                                             F Cl                                                    (14)                                                                              C.sub.3 H.sub.7                                                                          1                                                                                 ##STR25##                                                                             H F                                                     (15)                                                                              C.sub.2 H.sub.5                                                                          0 --      H Cl                                                    (16)                                                                              C.sub.4 H.sub.9                                                                          0 --      H Cl                                                    (17)                                                                              C.sub.6 H.sub.13                                                                         0 --      H Cl                                                    (18)                                                                               ##STR26##                                                                               0 --      F Cl C 96 N 142 I, Δε = 10.3              (19)                                                                              C.sub.3 H.sub.7                                                                          1                                                                                 ##STR27##                                                                             H Cl                                                    (20)                                                                              C.sub.5 H.sub.11                                                                         1                                                                                 ##STR28##                                                                             H Cl                                                    __________________________________________________________________________

EXAMPLE 21

According to Scheme II given above 1-(4-chloro-3-fluorophenyl)-2-(4-(5-propyldioxane-2-yl)-phenyl)-ethane is obtained from 1-(4-chloro-3-fluorophenyl)-2-(4-bromophenyl)-ethane and 2-(hydroxymethyl)-pentan-1-ol.

EXAMPLES 22 TO 24

The following compounds are obtained analogously

    ______________________________________                                         R.sup.1    n      Q.sup.2          L    Y                                      ______________________________________                                         (22)  C.sub.5 H.sub.11                                                                        1                                                                                      ##STR29##     F    Cl                                   (23)  C.sub.5 H.sub.11                                                                        1                                                                                      ##STR30##     H    Cl                                   (24)  C.sub.5 H.sub.11                                                                        1                                                                                      ##STR31##     F    F                                    ______________________________________                                    

EXAMPLE 25

According to Scheme III given above 1-(4'-chloro-3'-fluorobiphenyl-4-yl)-2-(5-propyldioxane-2-yl)-ethane is obtained from 3-(4'chloro-3'-fluorobiphenyl-4-yl)-proponaldehyde and 2-(hydroxymethyl)-pentan-2-ol.

EXAMPLES 26 TO 28

The following compounds obtained analogously:

    ______________________________________                                         R.sup.1    n      Q.sup.2          L    Y                                      ______________________________________                                         (26)  C.sub.5 H.sub.11                                                                        1                                                                                      ##STR32##     F    Cl                                   (27)  C.sub.5 H.sub.11                                                                        1                                                                                      ##STR33##     H    Cl                                   (28)  C.sub.5 H.sub.11                                                                        1                                                                                      ##STR34##     F    F                                    ______________________________________                                    

EXAMPLE 29

Mixture (A) contains: ##STR35## and exhibits N 72 I, Δε+0.06, n=0.1139

Mixture (B) contains 90% of mixture (A) and 10% of ##STR36## and exhibits N 65.2 I, Δε=+1.04, Δn=0.1097.

EXAMPLE 30

Mixture (C) contains 90% of mixture (A) and 10% of ##STR37## and exhibity N 60.1 I, Δε=+1.24, Δn=0.1076.

EXAMPLE 31 Preparation of 1(trans-4-Propylcyclohexyl)-2-[-(4-chlorophenyl)-dioxane-5-yl]-ethane ##STR38## The trans-4-propylcyclohexylmethyleyanide (0.1 mole), NAOH (0.39 moles) and water (20 ml) are refluxed in digol (100 ml) for 30 hours. The reaction mixture is added, at 50° C., to water acidified and the product extracted into dichloromethane. The combined organic layers are washed with water, dried and the solvent removed. The crude acid is recrystallised from 7 vols of petrol ether (60-80˜). ##STR39##

A solution of the 2-(trans-4-propyleyclohexyl)- acetic acid (0.1 moles) of STEP 1 in ether (8.0 moles) is slowly added to a mixture of LiAlH₄ (0.211 moles) in dry ether (200 ml) at such a rate to give a gentle reflux. The mixture is then stirred for a further 3 hours. Excess LiAlH₄ is destroyed with ethyl acetate: ether (1:1) at 10° C. Dilute HCl is added and the product extracted into ether, washed with water and dried. After removal of the solvent the product was distilled under high vacuum. ##STR40## The (2-trans-4-propylcyclohexyl)-ethyl alcohol (0.1 moles) is refluxed in a mixture of HBr (50 ml) and H₂ SO₄ (10 ml). Water is added and the product extracted into dichloromethane. The crude bromide is distilled under high vacuum. ##STR41## To a solution of sodium ethoxide (made from Na in 70 ml IMS) is added diethyl malonate (0.105 moles), followed by the 2-(trans-4-propylcyclohexyl)-ethyl bromide (0.1 moles) of Step Three at 50° C. The mixture is refluxed for 4 hours and then the solvent removed. Water is added and the product extracted into ether and purified by distillation. ##STR42## The 2-(trans-4-propylcyclohexyl)-ethyl (0.1 moles) of STEP 3 in THF (50 ml) is slowly added to LiAlH₄ (0.114 moles) in THF (75 ml) at 40° C. under nitrogen. The mixture is refluxed for a further 4 hours and the excess LiAlH₄ is destroyed with dilute solution of water in THF. Sodium carbonate (12 g) in water (35 ml) is added at 80° C. After cooling to room temperature the solids are removed by filtration and the solvent removed. The product is then distilled under high vacuum. ##STR43## The 4-(trans-4-propylcyclohexyl)-2-(hydroxymethyl)-butane-2-ol (0.1 moles of STEP 5 is refluxed in toluene (220 ml) with the p-chloro-benzaldehyde (0.1 moles) and toluene sulphonic acid (0.8 g). Water being removed using a Dean Stark apparatus. After 3 hours at reflux the mixture is cooled and washed wit aq. NaHCO₃ then water, dried and the solvent evaporated. The crude product is chromatographed over silica gel and recrystallised from methanol.

EXAMPLES 32 TO 48

In place of the used trans-4-propylcyclohexylmethylcyanide and the p-chloro-benaldehyde other homologues cyclohexylmethyleyanides and benzaldehydes can be used for preparation of the following compounds in analogy to example 25:

    ______________________________________                                          ##STR44##                                                                            n           L.sup.1   Y                                                 ______________________________________                                         (32)     5             H         Cl                                            (33)     7             H         Cl                                            (34)     3             F         Cl                                            (35)     5             F         Cl                                            (36)     7             F         Cl                                            (37)     3             F         F                                             (38)     5             F         F                                             (39)     7             F         F                                             (40)     5             H         OCF.sub.3                                     (41)     5             H         CF.sub.3                                      (42)     5             H         CN                                            (43)     5             H         F                                             (44)     5             F         OCF.sub.3                                     (45)     5             F         CF.sub.3                                      (46)     3             F         CN                                            (47)     5             F         CN                                            (48)     7             F         CN                                            ______________________________________                                    

EXAMPLE 49

Preparation of 1-(4-Pentyloxyphenyl)-2-[2-(4-cyanophenyl)]-ethane ##STR45## The 2-(4-Pentyloxyphenyl)-ethanol (0.1 moles/obtained from benzylcyanide in an analogous way to Example 1 STEP 1/2) is stirred in pyridine (35 ml) and toluene sulphonyl chloride (0.125 moles). Dilute HCl is added and the product is filtered under vacuum, washed with water and recrystallised from 2 volumes of methanol at 3° C. ##STR46## To a solution of sodium methoxide (made from Na in 7o ml (MS) is added diethyl malenate (0.105 moles), followed by the tosylate of STEP 1 (0.1 moles). The product is obtained analogously to Example 1 STEP 4. ##STR47## The diester (0.1 moles) of STEP 2 is reduced with LiAlH₄, analogously to Example 1 STEP 5 and condensed with p-formylbenzonitrile (0.1 moles) with toluene sulphonic acid in a Dean and Stark trap in analogy to Example 1 STEP 6.

EXAMPLES 50 TO 70

In place of the used 2-(4-pentyloxyphenyl)-ethanol and p-formylbenzonitrile other homologue 2-phenylethanoles and benzaldehydes can be used for preparation of the following compounds in analogy to example 43:

    ______________________________________                                          ##STR48##                                                                     Example     R.sup.1   L.sup.1 L.sup.2                                                                              Y                                          ______________________________________                                         (50)        H.sub.7 C.sub.3                                                                          H       H     CN                                         (51)        H.sub.11 C.sub.5                                                                         H       H     CN                                         (52)        H.sub.7 C.sub.3 O                                                                        F       H     CN                                         (53)        H.sub.11 C.sub.5                                                                         F       H     CN                                         (54)        H.sub.11 C.sub.5                                                                         H       F     CN                                         (55)        H.sub.11 C.sub.5 O                                                                       H       H     F                                          (56)        H.sub.7 C.sub.3                                                                          H       H     F                                          (57)        H.sub.7 C.sub.3 O                                                                        H       H     F                                          (58)        H.sub.11 C.sub.5                                                                         F       H     F                                          (59)        H.sub.11 C.sub.5                                                                         H       F     F                                          (60)        H.sub.9 C.sub.4 O                                                                        H       H     Cl                                         (61)        H.sub.7 C.sub.3                                                                          H       H     Cl                                         (62)        H.sub.11 C.sub.5                                                                         H       H     Cl                                         (63)        H.sub.7 C.sub.3 O                                                                        H       H     Cl                                         (64)        H.sub.11 C.sub.5                                                                         F       H     Cl                                         (65)        H.sub.11 C.sub.5                                                                         H       F     Cl                                         (66)        H.sub.11 C.sub.5                                                                         H       H     OCF.sub.3                                  (67)        H.sub.11 C.sub.5                                                                         H       H     CF.sub.3                                   (68)        H.sub.11 C.sub.5                                                                         H       F     OCF.sub.3                                  (69)        H.sub.11 C.sub.5                                                                         F       H     CF.sub.3                                   (70)        H.sub.11 C.sub.5                                                                         F       H     OCF.sub.3                                  ______________________________________                                    

EXAMPLE 71

Mixture (D) contains ##STR49## and exhibits N 69.1 I, V₉₀ 2.24 Volt (measured in a 90° TN cell).

EXAMPLE 72

Mixture (E) contains ##STR50## and exhibits N 71 I, V₉₀ 2.37 Volt (measured in a 90° TN cell).

EXAMPLE 73

Mixture (F) contains ##STR51## and exhibits

N 94 I, η 19.6 cSt, Δn 0.139 and V₉₀ of 2.809 Volts in a 240° STN cell. 

We claim:
 1. A phenyldioxane of formula I ##STR52## wherein R¹ is alkyl residue with up to 16 C atoms, wherein one or two nonadjacent CH₂ groups may be replaced by --O--, --S--, --CO--O--, or --O--CO--,Q¹ and Q² are each independently ##STR53## L¹ and L² are each independently F or H, and Y is Cl or F m and n are 0 or 1with the provisos that a) in the case that m is 0, m is 1 and Q¹ is ##STR54## one of L¹ and L² is F and Y is Cl or F and b) in the case that n is 1, m is 0 and Q² is ##STR55## one of L¹ and L² is F or L¹ and L² are H and Y is Cl.
 2. A phenyldioxane according to claim 1 wherein m is O and Y is Cl or in the case that L¹ or L² is F also F.
 3. A phenyldioxane according to claim 1 wherein n is O, m is 1 and Q¹ is ##STR56##
 4. A phenyldioxane of claim 2 whereinR¹ have the meaning given, Q² is ##STR57## n is 1, and Y is Cl.
 5. A phenyldioxane according to claim 3 wherein R¹, L¹ and L² have the meaning given, ##STR58## and Y is Cl.
 6. A phenyldioxane according to claim 1 of the part formulae I1a to I1h: ##STR59##
 7. A phenyldioxane according to claim 1 of the part formulae I2a to I2f: ##STR60##
 8. A phenyldioxane according to claim 7 of the part formulae I2a to I2c, wherein Y is Cl.
 9. A phenyldioxane according to claim 1 of the part formulae I2g, I2h, I2k or I2l: ##STR61##
 10. A phenyldioxane according to claim 9 or the part formulae I2g or I2h, wherein ##STR62## 